A meta-analysis of severity and yield loss from ascochyta blight on field pea in Western Australia

A meta-analysis of severity and yield loss from ascochyta blight (AB) on field pea was performed using 18 field experiments conducted over eight seasons in 13 locations in Western Australia (WA). The severity of AB, across the WA grain-belt, reached its maximum limit (AB severity 5) during mid-April sowing and linearly declined to almost nil by mid-July sowing. Pre-sowing rainfall had a significant effect on AB severity: the more rainfall events that occurred the less was the disease severity. The regional and seasonal difference in the rate of decline of the AB severity (slope of the regression line) with delay in sowing was not significant, whereas the intercepts were largely significant indicating there were differences in the initial AB severity status between the regions and seasons. Fungicide control [Impact® in-furrow (flutriafol) application or fortnightly sprays of Bravo® (chlorothalonil)] did not reduce the disease severity in early sowing (week ending 7 May). The yield loss due to AB was calculated as 10.3% per AB severity unit, indicating that a loss of ≥50% could occur with the highest severity. Magnet showed significantly higher yield loss compared to all other varieties. The differences in yield loss between the five regions were not significant. On the other hand, a dry finishing season resulted in significantly higher yield loss than a wet finishing season. These analyses will help design improved strategies for AB management in field pea in Western Australia.